NSA analysts have “an extraordinarily difficult job, one in which actions are second-guessed, success is unreported and failure can be catastrophic,” he said. They “know that if another 9/11 or massive cyberattack occurs, they will be asked, by Congress and the media, why they failed to connect the dots.” They have been doing this job without any known abuse of power. None of this is news, but it was valuable — to the country and undoubtedly to the people who do this work — to hear the president say so.

Mr. Obama also rightly paid respect to both sides of the debate. Those who defend the status quo “are not dismissive of civil liberties,” he said. By the same token, “those who are troubled by our existing programs are not interested in repeating the tragedy of 9/11.” Again not groundbreaking, perhaps, but important for the president to say.

Americans send sensitive personal information over electronic media every day that computers can easily gather and crank through. This is not the world in which foreign intelligence policy was established in the 1970s, nor even when lawmakers reviewed it in the past decade. People will naturally feel uneasy about what government can quickly learn about them and will demand limits.

“The challenge is getting the details right, and that’s not simple,” the president said. That much is apparent from the reforms the president proposed, which attempt to strike a better balance between these competing equities, but which lack critical specifics. The president said he favors new rules restricting the collection, warehousing and use of Americans’ communications picked up under surveillance authorities that are supposed to be aimed abroad. But he punted the formulation of those rules to the director of national intelligence and the attorney general. Mr. Obama endorsed eliminating the government’s bulk collection of phone records while preserving its capability to learn from those records, but he didn’t map out how that will work. He asked lawmakers to create a panel of attorneys who could argue “significant” cases independently of the government before the secretive Foreign Intelligence Surveillance Act court, but he didn’t explain who would decide which cases were “significant.”

Missing entirely was any reference to needed reforms to cordon off Americans’ data stored on cloud services such as e-mail and online word processors, to which badly outdated federal law fails to afford common protections. Also missing was a discussion of how much the NSA should be meddling with Internet encryption standards, about which U.S. tech companies care deeply.

The president struck a productive tone on Friday. But it will take a lot more time, it seems, to engage in the unsimple task of filling in the details.

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